Summary still there in animation dope sheet
I don't believe it can be cleared. But it's of no consequence. The Summary is simply an expandable section which gives you a general, at-a-glance view of your keyframe data. It really has no purpose until you have keyframes. So maybe it shouldn't appear until you do. But it's always there regardless. In any case, once you have keyframes, they can all be collapsed under the Summary section. It seems to only exist in the Dope Sheet and the Timeline. If you're seeing it in the Dope Sheet, the top row of keyframes comes from the Summary section. It is very useful, because it lets you move every keyframe from a certain time location at once, irrespective of whatever channel any of those keyframes are actually found.